The Grumman F6F Hellcat is an American carrier-based fighter aircraft of World War II. Designed to replace the earlier F4F Wildcat and to counter the Japanese Mitsubishi A6M Zero, it was the United States Navy's dominant fighter in the second half of the Pacific War. In gaining that role, it prevailed over its faster competitor, the Vought F4U Corsair, which initially suffered from several carrier-operating issues, including poor forward visibility, landing bounce and stall characteristics.
Powered by a Pratt & Whitney R-2800 Double Wasp, the same powerplant used for both the Corsair and the USAAF Republic P-47 Thunderbolt fighters, the F6F was an entirely new aircraft that retained only a general resemblance to the earlier Wildcat.Thruelsen 1976, p. 135. Some military observers tagged the Hellcat as the "Wildcat's big brother".Sullivan 1979, p. 4.
The F6F made its combat debut on 31 August 1943 during raids on Marcus Island. It subsequently established itself as a rugged, well-designed carrier fighter, which was able to outperform the A6M Zero and played a major role in helping the U.S. gain air superiority in the Pacific. In total, 12,275 were built in just over two years.Kinzey 1996, p. 4.
Hellcats were credited with destroying a total of 5,223 enemy aircraft while in service with the U.S. Navy, U.S. Marine Corps, and Royal Navy Fleet Air Arm (FAA).Tillman 1996, p. 81. This was more than any other Allied naval aircraft. After the war, Hellcats were phased out of front-line service in the US, but radar-equipped F6F-5Ns remained in service as late as 1954 as night fighters.
Design and development
XF6F
Grumman had been working on a successor to the F4F Wildcat since 1938, and the contract for the prototype XF6F-1 was signed on 30 June 1941. The aircraft was originally designed to use the Wright R-2600 Twin Cyclone two-row, 14-cylinder radial engine of (the same engine used with Grumman's then-new torpedo bomber under development), driving a three-bladed Curtiss Electric propeller.Kinzey 1996, p. 16. Instead of the Wildcat's narrow-track, hand-cranked, main landing gear retracting into the fuselage inherited from the F3F (a design from the 1930s Grumman FF-1 fighter biplane), the Hellcat had wide-set, hydraulically actuated landing-gear struts that rotated through 90° while retracting backwards into the wings, with full wheel doors fitted to the struts that covered the entire strut and the upper half of the main wheel when retracted, and twisted with the main gear struts through 90° during retraction. The wing was mounted lower on the fuselage and was able to be hydraulically or manually folded, with each panel outboard of the undercarriage bay folding backwards from pivoting on a specially oriented, Grumman-patented "Sto-Wing" diagonal axis pivoting system much like the earlier F4F, with a folded stowage position parallel to the fuselage with the leading edges pointing diagonally down.Kinzey 1987, p. 14.
Throughout early 1942, Leroy Grumman, along with his chief designers Jake Swirbul and Bill Schwendler, worked closely with the U.S. Navy's Bureau of Aeronautics (BuAer) and experienced F4F pilots,Thruelsen 1976, p. 166. to develop the new fighter in such a way that it could counter the Zero's strengths and help gain air dominance in the Pacific Theater of Operations.Ewing 2004, p. 182. On 22 April 1942, Lieutenant Commander Butch O'Hare toured the Grumman Aircraft company and spoke with Grumman engineers, analyzing the performance of the F4F Wildcat against the Mitsubishi A6M Zero in aerial combat.Ewing 2004, p. 86. BuAer's Lt Cdr A. M. Jackson directed Grumman's designers to mount the cockpit higher in the fuselage.Francillon 1989, p. 200. In addition, the forward fuselage sloped down slightly to the engine cowling, giving the Hellcat's pilot good visibility.Kinzey 1996, p. 6.
Change of powerplant Based on combat accounts of encounters between the F4F Wildcat and A6M Zero, on 26 April 1942, BuAer directed Grumman to install the more-powerful, 18-cylinder Pratt & Whitney R-2800 Double Wasp radial engine – which was already in use with Chance Vought's Corsair since 1940 – in the second XF6F-1 prototype.Ewing and Lundstrom 2004, pp. 155, 156. Grumman complied by redesigning and strengthening the F6F airframe to incorporate the R-2800-10, driving a three-bladed Hamilton Standard propeller. With this combination, Grumman estimated the XF6F-3s performance would increase by 25% over that of the XF6F-1. The Cyclone-powered XF6F-1 (02981) first flew on 26 June 1942, followed by the first Double Wasp-equipped aircraft, the XF6F-3 (02982), which first flew on 30 July 1942. The first production F6F-3, powered by an R-2800-10, flew on 3 October 1942, with the type reaching operational readiness with VF-9 on in February 1943.Kinzey 1987, p. 6.
Further development
The F6F series was designed to take damage and get the pilot safely back to base. A bullet-resistant windshield was used and a total of of cockpit armor was fitted, along with armor around the oil tank and oil cooler. A self-sealing fuel tank was fitted in the fuselage. Standard armament on the F6F-3 consisted of six .50 BMG (12.7 mm) AN/M2 Browning air-cooled machine guns with 400 rounds per gun. A center-section hardpoint under the fuselage could carry a single disposable drop tank, while later aircraft had single bomb racks installed under each wing, inboard of the undercarriage bays; with these and the center-section hard point, late-model F6F-3s could carry a total bomb load in excess of . Six High Velocity Aircraft Rockets (HVARs) could be carried – three under each wing on "zero-length" launchers.Sullivan 1979, pp. 24, 30, 33.Parsch, Andreas. "5 inch FFAR/HVAR." designation-systems.net, 2010. Retrieved: 28 October 2012.
Two night-fighter subvariants of the F6F-3 were developed; the 18 F6F-3Es were converted from standard-3s and featured the AN/APS-4 10 GHz frequency radar in a pod mounted on a rack beneath the right wing, with a small radar scope fitted in the middle of the main instrument panel and radar operating controls installed on the port side of the cockpit.Kinzey 1996, pp. 30–31. The later F6F-3N, first flown in July 1943, was fitted with the AN/APS-6 radar in the fuselage, with the antenna dish in a bulbous fairing mounted on the leading edge of the outer right wing as a development of the AN/APS-4; about 200 F6F-3Ns were built.Kinzey 1996, pp. 28–29. Hellcat night fighters claimed their first victories in November 1943.Green 1975, p. 91. In total, 4,402 F6F-3s were built through until April 1944, when production was changed to the F6F-5.
The F6F-5 featured several improvements, including a more powerful R-2800-10W engine employing a water-injection system and housed in a slightly more streamlined engine cowling, spring-loaded control tabs on the ailerons, and an improved, clear-view windscreen, with a flat armored-glass front panel replacing the F6F-3's curved plexiglass panel and internal armor glass screen.Taylor 1969, p. 503. In addition, the rear fuselage and tail units were strengthened, and apart from some early production aircraft, most of the F6F-5s built were painted in an overall gloss sea-blue finish.Kinzey 1996, pp. 6–7. After the first few F6F-5s were built, the small windows behind the main canopy were deleted.Kinzey 1996, p. 7. The F6F-5N night-fighter variant was fitted with an AN/APS-6 radar in a fairing on the outer-starboard wing. A few standard F6F-5s were also fitted with camera equipment for reconnaissance duties as the F6F-5P.Green 1975, pp. 93–94. While all F6F-5s were capable of carrying an armament mix of one 20-mm (.79-in) M2 cannon in each of the inboard gun bays (220 rounds per gun), along with two pairs of .50-in (12.7-mm) machine guns (each with 400 rounds per gun), this configuration was only used on later F6F-5N night fighters.Kinzey 1987, p. 27. The F6F-5 was the most common F6F variant, with 7,870 being built.
Other prototypes in the F6F series included the XF6F-4 (02981, a conversion of the XF6F-1 powered by an R-2800-27 and armed with four 20-mm M2 cannon), which first flew on 3 October 1942 as the prototype for the projected F6F-4. This version never entered production and 02981 was converted to an F6F-3 production aircraft.Kinzey 1996, p. 32. Another experimental prototype was the XF6F-2 (66244), an F6F-3 converted to use a Wright R-2600-15, fitted with a Birman-manufactured mixed-flow turbocharger, which was later replaced by a Pratt & Whitney R-2800-21, also fitted with a Birman turbocharger.White 2001, pp. 260, 508. The turbochargers proved to be unreliable on both engines, while performance improvements were marginal. As with the XF6F-4, 66244 was soon converted back to a standard F6F-3.Kinzey 1996, pp. 17–18. Two XF6F-6s (70188 and 70913) were converted from F6F-5s and used the 18-cylinder Pratt and Whitney R-2800-18W two-stage supercharged radial engine with water injection and driving a Hamilton-Standard four-bladed propeller.Kinzey 1996, pp. 50–51. The XF6F-6s were the fastest version of the Hellcat series with a top speed of , but the war ended before this variant could be mass-produced.Sullivan 1979, p. 46. The last Hellcat rolled out in November 1945, the total production being 12,275, of which 11,000 had been built in just two years.Winchester 2004, p. 110. This high production rate was credited to the sound original design, which required little modification once production was under way.
Operational history
U.S. Navy and Marines The U.S. Navy greatly preferred the more docile flight characteristics of the F6F over the Vought F4U Corsair, despite the Corsair's superior speed. This preference was particularly evident during carrier landings, which were a critical requirement for the Navy's success. Consequently, the Navy transferred the Corsair to the Marine Corps, which, not having to worry about carrier landings, utilized the Corsair for land-based sorties. The Hellcat remained the standard carrier-borne fighter for the U.S. Navy until the F4U series was finally cleared for U.S. carrier operations in late 1944. By that time, the carrier landing issues had largely been resolved, thanks in part to the Royal Navy Fleet Air Arm's use of the Corsair, which began in 1943.Styling 1995, p. 67. In addition to its good flight qualities, the Hellcat was easy to maintain and had an airframe tough enough to withstand the rigors of routine carrier operations.Tillman 1996, p. 6. Like the Wildcat, the Hellcat was designed for ease of manufacturing and ability to withstand significant damage.
The Hellcat first saw action against the Japanese on 1 September 1943, when fighters off shot down a Kawanishi H8K "Emily" flying boat.Dean 1997, p. 559. Soon after, on 23 and 24 November, Hellcats engaged Japanese aircraft over Tarawa, shooting down a claimed 30 Mitsubishi Zeros for the loss of one F6F. Over Rabaul, New Britain, on 11 November 1943, Hellcats and F4U Corsairs were engaged in day-long fights with many Japanese aircraft, including A6M Zeros, claiming nearly 50 aircraft.
When trials were flown against a captured Mitsubishi A6M5 model Zero, they showed that the Hellcat was faster at all altitudes. The F6F out-climbed the Zero marginally above and rolled faster at speeds above , however, the Japanese fighter could out-turn its American opponent with ease at low speed, and enjoyed a slightly better rate of climb below . The trials report concluded:
Hellcats were the major U.S. Navy fighter type involved in the Battle of the Philippine Sea, where so many Japanese aircraft were shot down that Navy aircrews nicknamed the battle the "Great Marianas Turkey Shoot". The F6F accounted for 75% of all aerial victories recorded by the U.S. Navy in the Pacific.Tillman 1979, p. 9. Radar-equipped Hellcat night-fighter squadrons appeared in early 1944.